1. Field of the Invention
This invention relates to modifying polyhedral oligomeric silsesquioxane (POSS) compounds, particularly methods for controlling the stereo chemistry of functionalities or X groups to desired positions on POSS compounds and also to methods for inserting one or more ring substituents, other than silicon, into a POSS compound.
2. Description of Related Art
Recent art in the silsesquioxane field has taught processes for the chemical manipulation of the organic functionalities (substituents, e.g., denoted by R) contained on the silicon oxygen frameworks of polyhedral oligomeric silsesquioxanes (POSS). While these methods are highly useful for varying the organic functionalities contained on POSS molecules, they do not offer the ability to cleave and/or manipulate the silicon-oxygen frameworks of such compounds. Thus, these methods are of no utility for transforming the multitude of readily available polyhedral oligomeric silsesquioxanes systems into useful compounds that can be subsequently utilized for a multitude of catalysis and material applications.
Earlier art has reported that bases (e.g. NaOH, KOH, etc.) could be used to (1) catalyze the polymerization of polyhedral oligomeric silsesquioxanes into partly networked resins, (2) convert polysilsesquioxane resins into discrete polyhedral oligomeric silsesquioxane structures and (3) catalyze the redistribution of selected fully condensed polyhedral oligomeric silsesquioxane structures into other related fully condensed polyhedral oligomeric silsesquioxane structural types. While the base assisted/catalyzed method does afford the manipulation of silicon-oxygen frameworks, it is not effective at selectively producing incompletely condensed frameworks from completely condensed species. This limitation results from the intolerance of the silicon-oxygen framework present in polyhedral oligomeric silsesquioxanes to base.
Accordingly there is need and market for a method for opening and/or substituting on POSS rings that overcomes the above prior art shortcomings.
There has now been discovered a method that rapidly and effectively opens the silicon-oxygen frameworks of POSS compounds to produce species that can subsequently be converted to various functionalized POSS compounds.
Broadly the present invention provides a method for controlling the stereo chemistry of X groups to exo or endo positions on a polyhedral oligomeric silsesquioxane (POSS) compound including, adding reagents selected from the group of a) CF3SO3H then H2O, b) Me3SnOH then HCl aq. and c) HBF4/BF3 then Me3SnOH then HCl aq, to the X groups to change one or more positions thereof to endo or exo, wherein the POSS compound is of the formula [(RSiO1.5)m(RXSiO1.0)n]xcexa3#, n=4-24, m=1-12, #=m+n, R is aliphatic, aromatic, olefinic, alkoxy, siloxy or H and the X groups are selected from the type of OH, OSO2 CF3, OSO2CH3, F, Cl, I, Br, Me3SnO, alkoxy and siloxy. Also provided are the POSS species formed by the above inventive method.
The invention further provides a method for inserting a ring substituent into a polyhedral oligomeric silsesquioxane (POSS) compound to produce a formula of the type [(RSiO 1.5)m(RSiO1.0)n(E)j]xcexa3#. This includes, reacting [(RSiO1.5)m(RXSiO1.0)n]xcexa3#, with a reagent selected from the group of H2NR, RB(OH)2, K2CrO4, R4NHSO4 and H2PR to obtain at least one expanded POSS ring in [(RSiO1.5)m(RSiO1.0)n(E)j]xcexa3#, where n is 4-24, m is 1-12, j is 1-8, # is m+n+j, R is aliphatic, aromatic, olefinic, alkoxy, siloxy or H, X is selected from the group of OSO2CF3, OSNMe3, OH, OSO2Cl, OSO2CH3, OS3H and halide and E is a ring substituent replacement for oxygen selected from the group of NR, PR, CrO4, SO4, O2BR, O2PR and O2P(O)R. Also provided are the POSS species formed by such inventive method.
For the purposes of explaining this invention""s processes and chemical compositions the following definition for representations of nanostructural-cage formulas is made:
Polysilsesquioxanes are materials represented by the formula [RSiO1.5]∞ where ∞=degree of polymerization within the material and R=organic substituent (H, cyclic or linear aliphatic or aromatic groups that may additionally contain reactive functionalities such as alcohols, esters, amines, ketones, olefins, ethers or halides). Polysilsesquioxanes may be either homoleptic or heteroleptic. Homoleptic systems contain only one type of R group while heteroleptic systems contain more than one type of R group.
POSS nanostructure compositions are represented by the formula:
[(RSiO1.5)n]xcexa3# for homoleptic compositions
[(RSiO1.5)m(RSiO1.5)n]xcexa3# for heteroleptic compositions
[(RSiO1.5)m(RXSiO1.0)n]xcexa3# for functionalized heteroleptic compositions
[(RSiO1.5)m(RSiO1.0)n(E)j]xcexa3# for heterofunctionalized heteroleptic compositions
[(XSiO1.5)]xcexa3# for homoleptic silicate compositions
In all of the above R is the same as defined above and X includes OH, Cl, Br, I, alkoxide (OR), acetate (OOCR), peroxide (OOR), amine (NR2) isocyanate (NCO), and R. The symbol E refers to elements within the composition that include (silanes and silicones e.g. SiR2, SiR2OSiR2OSiR2), (metals and nonmetals e.g. CrO2, PO2, SO2, NR) The symbols m, n and j refer to the stoichiometry of the composition. The symbol xcexa3 indicates that the composition forms a nanostructure and the symbol # refers to the number of silicon atoms contained within the nanostructure. The value for # is usually the sum of m+n or m+n+j. It should be noted that xcexa3# is not to be confused as a multiplier for determining stoichiometry, as it merely describes the overall nanostructural characteristics of the POSS system (aka cage size).
By xe2x80x9cstrong acidxe2x80x9d, as used herein, is meant one with a pKa number ranging from xe2x88x927 to 5 and is inclusive of superacids which cannot be assigned pKa values but which are characterized by Hammett acidity values H0 that range from 30 to 2.0 with the preferred range being 8-16.
Thus the present invention discloses methods that enable the selective manipulation of the silicon-oxygen frameworks in polyhedral oligomeric silsesquioxane (POSS) cage molecules. It is desired to selectively manipulate the frameworks of POSS compounds because they are useful as intermediate chemical agents that can be further converted or incorporated into a wide variety of chemical feed-stocks useful for the preparation of catalyst supports, monomers, and polymers wherein they impart new and improved thermal, mechanical and physical properties to common polymeric materials.
Further the present invention teaches processes that enable the manipulation of the silicon-oxygen frameworks (the cage-like structure) of common polyhedral oligomeric silsesquioxane (POSS) compounds [(RSiO1.5)n]xcexa3# (where R=aliphatic, aromatic, olefinic, alkoxy, siloxy or H and n=4-24) into new POSS species bearing frameworks with functionalities (e.g. silanes, silylhalides, silanols, silylamines, organohalides, alcohols, alkoxides, amines, cyanates, nitriles, olefins, epoxides, organoacids, esters, and strained olefins) for grafting, polymerization, or catalysis reactions.
Also in contrast to the prior art, the invention provides for the development of acid catalyzed processes that rapidly and effectively open the silicon-oxygen frameworks of polyhedral oligomeric silsesquioxanes to produce species that can subsequently be converted into stable incompletely condensed POSS-silanol and related functionalized POSS compounds. The use of acid reagents is desirable because the silicon-oxygen frameworks in polyhedral oligomeric silsesquioxanes are more tolerant of acids and hence will not as readily polymerize to form random networks, ladder polymers or other resinous systems. Acid reagents are also desirable in that their selectivity, rate of action, and the extent of reaction with fully condensed silicon-oxygen frameworks can be controlled through concentration, acid strengths (pH), and the chemical nature of the acid and its conjugate base. The nature of the solvent medium can also impart control over the cage opening process. Manipulation of these process variables allows for the optimization of conditions by which the silicon-oxygen frameworks of polyhedral oligomeric silsesquioxanes such as [(RSiO1.5)n]xcexa3# (where R=aliphatic, aromatic, olefinic, alkoxy or siloxy or H and n=4-24) can be selectively manipulated to produce new polyhedral oligomeric silsesquioxanes with functionalized structures. The polyhedral oligomeric silsesquioxanes produced from the acid treatment processes can be used directly as reagents in polymerizations or they can be additionally derivatized through reaction with a variety of organosilanes or organic reagents such as amines, phosphines, transition metals, or tin complexes to form diverse new POSS chemical reagents.
Thus processes for the selective ring opening, stereochemical interconversion, expansion and reduction of the silicon oxygen frameworks in polyhedral oligomeric silsesquioxanes (POSS) to form new polyhedral oligomeric silsesquioxane chemical species have been developed. The selective ring-opening and stereochemical interconversion processes principally utilize strong acids (e.g., HBF4/BF3, CF3SO3H (trifluoromethanesulfonic acid), ClSO3H (chlorosulfonic acid), CH3SO3H (methanesulfonic acid), H2S04 (sulfuric acid), HClO4 (perchloric acid), etc.) to react with the silicon-oxygen-silicon framework""s (Sixe2x80x94Oxe2x80x94Si) bonds. Conditions in the processes can be controlled so that the Sixe2x80x94Oxe2x80x94Si frameworks are selectively cleaved to afford species containing Sixe2x80x94X bonds where X is the conjugate base of the respective strong acid (e.g., X=F, CF3SO3, ClSO3, HSO4, ClO4) or where X=OH. The resulting new polyhedral oligomeric silsesquioxane species can then undergo additional chemical manipulations, such as cage expansion or reduction to ultimately be converted into POSS-species bearing one or more functionalities suitable for polymerization reactions.
Examples of openable POSS systems are shown below. 
The invention provides for manipulation of silicon-oxygen frameworks in P0SS Systems. Such processes utilize acid reagents and POSS compounds[(RSiO1.5)n]xcexa3#, where R=organic substituent (H. cyclic or linear aliphatic, aromatic, olefinic, alkoxy or siloxy groups that can additionally contain reactive functionalities such as alcohols, esters, amines, ketones, olefins and ethers) and where n=an integer from 4 to 14 with n=6-12 being preferred. The processes allow for the conversion of low cost, easily produced polyhedral oligomeric silsesquioxanes of the formula [(RSiO1.5)n]xcexa3# to be converted into more desirable polyhedral oligomeric silsesquioxanes of the type [(RSiO1.5)m(RXSiO1.0)n]xcexa3# where m=1-12, n=4-24 and X=the weak conjugate base of the strong acid including F, OH, SH, NHR or NR2 (where R=as defined above), ClO4, SO4, SO3CF3, SO3Cl, SO3CH3, NO3, PO4, Cl or OH. Formulations of the type [(RSiO1.5)m(RXSiO1.0)n]xcexa3# can be used as stand-alone chemical reagents or further derivatized into a diverse number of other POSS chemical species.
Thus polyhedral oligomeric silsesquioxanes of the type [(RSiO1.5)6]xcexa36 (Formula 1) are readily converted using the above mentioned acids into formula [(RSiO1.5)4(RXSiO1.0)2]xcexa36, Formula 7 and [(RSiO1.5)2(RXSiO1.0)4]xcexa36, where Formula 8 and Formula 9 are geometrical isomers. Also a twisted cage can be formed per formula 7d. 
Also polyhedral oligomeric silsesquioxanes of the type [(RSiO1.5)8]xcexa38 (Formula 2) are readily converted using the above mentioned acids into formula [(RSiO1.5)6(RXSiO1.0)2]xcexa38, where Formula 10 and Formula 11 are geometrical isomers. 
Thus the present invention also provides processes that promote the structural rearrangement of silicon-oxygen frameworks, e.g., the conversion of Formula 1 to Formula 7d and of Formula 2 to Formula 11.
It is desirable to rearrange the silicon-oxygen frameworks in POSS systems in order to change the overall 3-dimensional topology of POSS molecules and thereby tailor their physical properties. Through rearranging the silicon-oxygen structural frameworks, improvements in mechanical properties such as tensile, compressive, abrasion resistance, modulus and thermal properties such as glass and melt transition temperatures as well as morphological and microstructural control can be better achieved in polymer systems which contain POSS.
The structural rearrangement of POSS""s silicon-oxygen frameworks involves the following sequence: opening of the silicon oxygen ring, rearrangement of the framework, closure of the framework. The processes in this disclosure describe the use of acidic reagents to open POSS""s silicon-oxygen rings and in some cases these same processes and conditions also promote the rearrangement of the rings. The closure of the rings usually involve the net elimination of at least one or more oxygen atoms from silicon-oxygen framework as compared to the original formula. For example, the conversion of formula 1 to formula 7d (or formula 2 into formula 11) necessarily involves the elimination of an oxygen atom from the framework. The oxygen atom that has been removed from the framework may either be eliminated entirely from the POSS molecule or it may be relocated external to the framework as a reactive functionality such as a silanol.
Polyhedral oligomeric silsesquioxanes of the type [(RSiO1.5)m(R3SiO1.5)n]xcexa3# [such as [(RSiO1.5)7(R3SiO1.5)1]xcexa38, Formula 6], where more than one type of R is contained within the same molecule and are readily converted, using the above mentioned acids, into a variety of isomers of formula [(RSiO1.5)6(RXSiO1.0)1(R3XSiO1.0)1]xcexa38, where Formula 12a, Formula 12b, and Formula 12c are all geometrical isomers. 
The action of the above mentioned acids and reagents can also be controlled in such a manner that the silicon atoms can be entirely removed from the silicon oxygen frameworks of polyhedral oligomeric silsesquioxanes. The process is especially effective when silisesquioxanes of the formula [(RSiO1.5)m(R3SiO1.5)n]xcexa3# [such as [(RSiO1.5)7(R3SiO1.5)1]xcexa38), Formula 6], which contain more than one type of R group, are utilized. In such cases formula of the type [(RSiO1.5)4(R3XSiO1.0)3]xcexa37 can be prepared. This represents an entirely new synthetic route for the preparation of the very useful incompletely condensed trisilanol reagents such as [(RSiO1.5)4(R3XSiO1.0)3]xcexa37 where X=OH in particular. Formulas 13a and 13b are stereochemical isomers. 
Polyhedral oligomeric silsesquioxanes of the type [(RSiO1.5)10]xcexa310 (Formula 3) and [(RSiO1.5)12]xcexa312 (Formula 4) are also readily converted using the above mentioned acids into formula [(RSiO 1.5)8(RXSiO1.0)2]xcexa310 (Formula 14a) or [(RSiO1.5)10(RXSiO1.0)2]xcexa312 where Formula 15a and Formula 15b are geometrical isomers. 
As is typical with chemical processes there are a number of variables that can be used to control the purity, selectivity, rate and mechanism of any process. Variables influencing the process for the cleavage and manipulation of silicon-oxygen frameworks in polyhedral oligomenic silsesquioxanes include the following: chemical class of acid, silicon-oxygen ring size, silicon-oxygen ring type [(RSiO1.5)m]xcexa3190, (silsesquloxane), [(RSiO1.5)m(RSiO1.0)n(R2Si)j]xcexa3# (silsesquioxane-siloxane), [(RSiO1.5)m(RSiO1.0)n(ROSi)j]xcexa3# (silsesquioxane-silicate), (where m=1-12 and n=4-24, j=1-8), effect of the organic substituents, process temperature, process solvent, process catalyst. Each of these variables is briefly discussed below. It is also envisioned that specific catalysts can be developed to promote or enhance the cage-opening action of the acids. Specifically, Lewis acids, including zinc compounds (e.g. ZnBr2, ZnCl2 and ZnF2 as well as SnCl4, SbCl5, FeCl3 and TiCl4) aluminum compounds (e.g. Al2H6, LiAlH4, AlI3, AlBr3, AlCl3 and AlF3) boron compounds (e.g. RB(OH)2, BI3, BBr3, BCl3 and BF3) are known to play important roles in the ring-opening polymerization of cyclic silicones in the ring-opening of polyhedral oligomeric silsesquioxanes.
Chemical Class of Acids
There are a number of strong acids that can be used to open the silicon-oxygen framework in POSS compounds. We have found that the acids such as HBF4 operating in the presence of BF3 are highly effective for cage-opening reactions. This acid is particularly effective for producing cage-opened products with exo-functionalities such as Formula 7-15 The effective ratio of HBF4/BF3 ranges from 0.25 to 10 with a ratio of 2.5 being preferred. The concentration of HBF4/BF3 can be varied and impacts both the extent and selectivity of the process. For example a deficiency of HBF4/BF3 to POSS is used to produce an POSS-exodifluoride product Formula 7 that has been side opened. The use of an excess of HBF4/BF3 to POSS, results in POSS-exotetrafluoride products Formula 8 and Formula 9 that have undergone two or more cage openings. Selectivity to produce singly cage-opened products can be carried out using a deficiency of HBF4/BF3 to POSS reagent in a 1.0 molar equivalents of HBF4 to 3.0 molar equivalents of BF3 ratio with a ratio of 1.5 being preferred. The HBF4/BF3 combination is effective at opening the silicon-oxygen frameworks at 24xc2x0 C. and 1 atmosphere, however it is recognized that variations in temperature and pressure can be used to either enhance or reduce the action of this system. It is also recognized that the use of other co-reagents such as BCl3, boron oxides, aluminum oxides, zinc oxides may be used in place of BF3 to promote the cage opening process through dehydration or other means.
Alternatively other strong acids and mixtures of strong acids can be utilized to carryout the cage-opening reactions. Classes of these acids include: sulfonic acids (e.g. HSO3CF3 triflic acid, HSO3Cl chlorosulfonic acid, HSO3CH3 methanesulfonic acid, and toluenesulfonic acids e.g. tosylates), superacids (e.g. HF/SbF5), mineral acids (e.g. HI, HBr, HCl, H2SO4, HNO3, HClO4). In some cases the anhydride of these acids may also be utilized provided that there is a trace amount of water present to generate a catalytic amount of the acid from the anhydride. This is particularly the case with triflic anhydride which is the anhydride of triflic acid. One advantage of using the anhydride over the acid is that the anhydride may facilitate the reaction by acting both as an acid source and as a dehydrating agent. This eliminates the need for co-reagents such as BF3 mentioned above.
There are additional advantages of using the above listed acids over the HBF4/BF3 system in terms of controlling the stereochemistry of the cage-opened product and the extent of reaction. For example triflic acid (and triflic anhydride) is effective at opening POSS compounds to form exo-[(RSiO1.5)m(R(F3CSO3)SiO1.0)n]xcexa3# complexes that upon undergoing hydrolysis can be used to produce POSS systems with endo stereochemistry (e.g. endo-[(RSiO1.5)m(R(HO)SiO1.0)n]xcexa3# compounds). When triflic acid or methanesulfonic acids are employed for the manipulation of the silicon oxygen frameworks in POSS cages, a 2-12 fold excess of the acid, relative to the molar equivalence of POSS, is suitable, with a 6 fold excess being preferred.
Silicon-oxygen Ring Size, Ring Type and Cage Sizes
The process discussed in this disclosure is not limited to specific sizes of POSS cages. As shown the process can be carried out on cages containing four to fourteen or more silicon atoms making up the silicon-oxygen framework. It has been noted that the silicon-oxygen ring size contained within such POSS systems does affect the rate at which cage opening can occur. For example rings containing three silicon atoms and three oxygen atoms as in Formula 1, appear to open faster than the larger rings containing 4 silicons and 4 oxygens (Formula 2). The relative rate for the opening of POSS silicon-oxygen rings appears to be six membered rings with three silicons greater than eight membered rings with four silicons greater than ten membered rings with five silicons greater than twelve membered rings with six silicons. Knowledge of this information allows the user of this process to control which silicon-oxygen rings within a POSS molecule will be opened. For example Formula 1 contains two six-membered rings and three eight membered silicon oxygen rings yet because the six membered rings within the molecule open at a faster rate than the eight membered rings, the molecule can be selectively functionalized at sites along the six membered ring to form Formula 7 and Formula 8.
Effect of the Organic Substituent, Process Solvents and Process Temperatures
The process described in this disclosure is not limited to POSS systems bearing specific organic groups (defined as R) attached to the silicon atom of the silicon-oxygen ring systems. The processes are amenable to opening the POSS systems bearing a wide variety of organic groups. The organic substituent does have a large effect on the solubility of both the final product and the starting POSS material. Therefore it is envisioned that the different solubilities between the starting POSS compounds and their respective cage-opened products can be used to facilitate the separation of and purification of the final reaction products. The process has been carried out in a wide range of solvents such as CCl4, CHCl3, CH2Cl2, fluorinated solvents, aromatics (halogenated and nonhalogenated), aliphatic (halogenated and nonhalogenated). The variables of solvent type, POSS concentration, and process temperature should be utilized in the standard way to match the specific cage opening process to the equipment available
Given the three dimensional and nanoscopic nature of POSS systems it is important to realize that a number of isomeric forms for any given formula can be produced by the methods of the invention. The stereochemistry of these isomers can be controlled by the inventive methods taught herein, however, in some cases geometrical isomers will still exist. A number of examples are provided to convey the presence of such isomers and that the invention is not limited to those stereochemical or geometrical isomers shown herein.
Examples of six isomers for difunctional incompletely condensed [(RSiO1.5)4(RXSiO1.0)2]xcexa36 systems are: 
Note that Formula 7 differs from formula 16 in that the silicon-oxygen framework of formula 7 has been cleaved along one of its six membered rings while formula 16 has been cleaved along one of its eight membered rings.
Examples of eight isomers for tetrafunctional twisted [(RSiO1.5)2(RSiO1.0)4]xcexa36 systems are: 
Examples of six isomers for tetrafunctional incompletely condensed [(RSiO1.5)2(RXSiO1.0)4]xcexa36 systems are: 
Examples of three isomers for difunctional twisted [(RSiO1.5)6(RXSiO1.0)2]xcexa38 systems are: 
Examples of twelve isomers for difunctional [(RSiO1.5)6(R3XSiO1.0)1(RXSiO1.0)1]xcexa38 systems are: 
The processes described above enable the manipulation of the silicon-oxygen frameworks within any POSS molecular structure. However it is advantageous to control the stereochemistry of the reactive functionalities now located on these molecules. Four general processes have now been identified to accomplish any type of stereochemical manipulation that is so desired. It is important to note that POSS molecules are three-dimensional nanostructured molecular systems and because of this the primary stereochemical considerations are whether the functionality in question is oriented externally or internally with respect to the center of a particular face (or side) of the cage. If a functionality is projected externally (away from) the center face of the cage it is referred to as having exo-stereochemistry while functionalities projecting toward the center of any face are referred to as having endo stereochemistry. Depending on the type of manipulation or desired use for the cage, it is of high value to the material manufacturer (chemist) to control the stereochemical nature of such products. Again these techniques can be used to control the stereochemistry of X functionalities on any size of POSS cage.
Method 1
Process for the Inversion of Stereochemistry
This method involves the hydrolysis of the X group on formulas 7, 10 to a silanol species of formulas 7, 10 with inversion of stereochemistry. The method is particularly useful for all X groups excluding fluoride. The method can also be utilized to alter the stereochemistry of silanol functionalized versions of formula 7, 10 and simply involves treatment of the silanol with HBF4 to form the intermediate species containing the conjugate base of the acid. Treatment of this species with acidic water reproduces the silanol species with inverted stereochemistry. The process can be used to convert both endo and exo stereochemical orientation of groups. The process is applicable to any size of POSS cage where n=4 to 14 in [(RSiO1.5)n]xcexa3#. 
Method 1 can be used to alter the stereochemistry of X groups on all sizes of polyhedral oligomeric silsesquioxane cages. The example below shows that the process can be carried out on POSS systems bearing six silicon atoms within the framework. 
In some instances it is possible to carry out the conversion process so formula-bearing mixed stereochemical (endo-exo) functionalities are formed. 
Method 2
A Two Step Process for the Retention of Stereochemistry.
This method is particularly useful for formula bearing X groups especially where X=F. The process involves the treatment of [(RSiO1.5)m(RFSiO1.0)n]xcexa3# first with trimethyltinhydroxide to form the species [(RSiO1.5)m(R(Me3SnOSiO1.0)n]xcexa3# followed by treatment in a second step with concentrated hydrochloric acid (or HCl aq., such as 1-12N and preferably 2-4N HCl) to produce a silanol species [(RSiO1.5)m(R(HO)SiO1.0)n]xcexa3# in which the silanol groups occupy the same stereochemical position relative to the F groups in the starting compound. The process is applicable to any size of POSS cage where n=4 to 14 in [(RSiO1.5)n]xcexa3#. 
Reactions of Formula 7a or 10a with Grignard reagents (RMgX) or hydride reducing agents (such as LiAlH4 and Al2H6) also proceed with inversion of stereochemistry to produce the corresponding di-exo species of Formulas 7a and 10a.
Method 2 can be used to alter the stereochemistry of X groups on all sizes of polyhedral oligomeric silsesquioxane cages. The example below shows that the process can be carried out on POSS systems bearing six silicon atoms within the framework. 
Reactions of Formula 7a or 10a with alkyllithium reagents (e.g., CH3Li, C6H5CCLi and CH2xe2x95x90CHLi) also proceed with retention of stereochemistry to produce the corresponding di-exo species of Formulas 7a and 10a.
Method 3
A Three Step Process for Inversion of Stereochemistry
A variation of the Method 2 process can be utilized to invert the stereochemistry of silanol groups. The method provides treatment of the silanol species [(RSiO1.5)m(R(HO)SiO1.0)n]xcexa3# with HBF4/BF3 to produce the [(RSiO1.5)m(R(F)SiO1.0)n]xcexa3# species followed by subsequent treatment with Me3SnOH and concentrated HCl as described above. The process is applicable to any size of POSS cage where n=4 to 14 in [(RSiO1.5)n]xcexa3#. 
Method 3 can be used to invert the stereochemistry of X groups on all sizes of polyhedral oligomeric silsesquioxane cages. The example below shows that the process can be carried out on POSS systems bearing six silicon atoms within the framework. 
Method 4
Combination of the Above Methods for Full Manipulation of X Groups and Stereochemistry.
The methods described for controlling the stereochemistry in these systems can also be effectively used in tandem to both vary the chemical nature of the X group in [(RSiO1.5)m(RXSiO1.0)n]xcexa3# systems as well as to interconvert the stereochemical nature of the X groups. Therefore any and all stereochemical isomers for the formulas described in this work are accessible and to be claimed. 
This section shows that the incompletely condensed POSS-silanols are very valuable reagents as they can be used to produce even more diverse POSS feedstocks. Examples are listed for expansion of formula 7, 8, 10. Note that in such processes formula bearing silanol groups with endo-stereochemistry are particularly useful for reacting with Y2SiR1R2 silane reagents where R1 and R2 are the same or different from the group previously defined for R (e.g. R1=H, methyl, ethyl, vinyl, allyl and phenyl) while Y=halides (e.g. Cl, Br, I) or amines such as NR2 (e.g. dimethylamine N(CH3)2, N(CH2CH3)2, etc.). The process of reacting formula 7 or formula 8 with either one or two equivalents of Y2SiR1R2 silane reagents results in a net expansion of the number of silicon atoms contained within the silicon oxygen framework of the original formula. In this manner the silicon-oxygen framework structures can be selectively enlarged as well as functionalized. This process is important because Formula 5 has undergone a formal expansion of the number of silicon atoms contained within its ring systems. Such an expansion is unprecedented and the rings now contain both (RSiO1.5) and (R2SiO) types of silicon atoms. Furthermore, functionalities useful for polymerizations and grafting can be incorporated into the molecule through the two organic R-groups located on the R2SiO silicon atom. 
This process can be used to expand the silicon-oxygen frameworks for all sizes of polyhedral oligomeric silsesquioxane cages. The example below shows that the process can be carried out on POSS systems bearing eight silicon atoms within the framework. 
The silicon-oxygen frameworks of compounds such as formula 10 can also be selectively expanded by atoms other than silicon. For examples Sn, S, N, P, B, and metals such as Cr, Ti, Zr, Ru, Mo, W, Pt, Pd, Al, Ga and Fe, can readily be incorporated into the silicon oxygen frameworks as indicated below. 
This shows that these cage-expanded compounds (formulas 19-21) can be utilized as chemical reagents to regenerate silanols or they can be used directly as reagents in grafting or polymerizations or as ligands. Note that in the case of using these reagents for the production of silanols, additional stereochemical control can be obtained with respect to whether endo or exo stereochemistry will result. For example treatment of Formula 19 or Formula 20 with concentrated hydrochloric acid produces two different stereochemical isomers of the same compound. 